7CP: Particles

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Lesson 1: ParticlesI am learning about the particle model to be able to explain properties of solids, liquids and gases

Ancient Greece: Democritus, a Greek philosopher sits on the beach watching the waves move against the sand. He notices that the tiny sand grains flow in and out as the waves flow over them. He thinks ‘If the grains of sand can flow like water then maybe the water is also made of tiny grains?’Over time he names these tiny uncuttable and invisible particles atoms, from the Greek atomos meaning uncuttable. He states that:

Everything is made of atoms There is empty space between atoms Atoms are indestructible Atoms always move

We now know that some of what Democritus thought is true and some is not. We know that atoms exist, but often they join together to make bigger clumps of atoms. We use the word “particle” to describe something really, really small. An atom is a particle, but a few atoms joined together is also a particle. So long as it is really tiny, we can call it a particle. In this unit we will look at how scientists draw particles and how drawing particles can help us understand why some substances are the way they are.Quick check

1. Who was Democritus?2. Name three objects made of atoms3. According to Democritus, could atoms be destroyed?4. Four atoms are joined together. What word could be used to describe these atoms?5. Is air made of atoms? Explain your answer. The 3 states of matter

All things made of atoms are called “matter.” Matter is grouped in 3 states: solid, liquid and gas. A good example is water:

Water as a solid is called ice Water as a liquid is called water or liquid water Water as a gas is called steam

The particles are the same in each state, but their arrangement is different. State Solid Liquid GasDiagram

Key features of diagram

Particles are all touchingRegular arrangementAll particles roughly the same sizeDraw at least 9Normally at the bottom of the box

Particles are all touchingRandom arrangementAll particles roughly the same sizeDraw at least 9Normally at the bottom of the box

Particles are not touchingRandom arrangementAll particles roughly the same sizeDraw at least 3Normally anywhere in the box

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In each of the states, the particles are exactly the same. All that is different about them is that they have different arrangements.6. Without looking at your table, draw a particle diagram of a solid, liquid and gas7. Below are a number of “wrong” examples of particle diagrams. Explain why each one is wrong. Your

answer should say something like “this is not a liquid because ______” or “this diagram is not good because ______”

The particles are held together by a force of attraction. In solids, the force has a high strength. This means the particles do not move away from each other. In gases, the force has a low strength. This means the particles can move away from each other. In liquids, the force has a medium strength. This means that the particles can move around, but they stay close to each other.This is why if you put a block of ice in a glass, it doesn’t immediately fall apart and fill up the glass. It stays like this:

but not this: With a liquid though, when you pour it into a glass, it spreads out in all directions like this:

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and not like this Gases are like liquids. The particles spread out in all directions. This is called flowing – when the particles move in all directions and start to fill up containers. Liquids and gases can flow. Solids cannot flow. Their particles do still move, but they vibrate on the spot. Their position does not change. 8. From memory, draw a particle diagram of a liquid and a solid9. What is water as a gas called?10. What is water as a solid called?11. Can a lump of solid metal flow? Why not?12. How strong are the forces between particles in a liquid?13. Complete the sentence stems below. Your teacher will explain how to do these.

In a solid, the particles cannot move because….In a solid, the particles cannot move but…In a solid, the particles cannot move therefore…

14. Now that your teacher has shown you how to do these, complete the stems:In a gas, the particles can move because….In a gas, the particles can move but…In a gas, the particles can move therefore…

15. A student says that particles in a solid do not move. Explain why the student is wrong. If you look at the diagram of a gas, there are big spaces between the particles. This means that if you had a box with a gas in, you could squeeze the box and make it smaller.

This is called “compressing.” The particles don’t get smaller, but the spaces between them do. In a solid and a liquid, the spaces between particles are so small that you can’t compress them. Gases can be compressed, solids and liquids can’t be compressed.16. Explain why liquids cannot be compressed17. A student has a substance that cannot be compressed, and does not flow. What type of substance

is it?18. A student says that when gases are compressed the particles get smaller. Explain why the student

is wrong. 19. A student says that liquids can be compressed because the particles can be made smaller. Explain

why the student is wrong. Properties

Whether something can be compressed or can flow is called a property. This is what something is like or how it behaves, and is normally something that we can see happening. Examples of properties:

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If it flowsIf it can be compressedIts colourThe temperature it turns into a liquidIf it is magneticIf it conducts (lets through) electricityIt is hardNotice that these are all things we can easily find out. Saying that something “has particles in an ordered arrangement” is not a property. This is the structure of the substance. Saying that something “has strong forces of attraction between the particles” is not a property. This is the bonding in the substance. You can’t look at a block of ice and know that the forces are strong or that the particles have an ordered arrangement. Scientists use bonding to explain structure which explains the properties. For example: In solids, the forces between particles have high strength, leading to a structure where particles cannot move. Therefore it has a property that it does not flow.

For a liquid, that would be:In liquids, the forces between particles have medium strength, leading to a structure where particles cannot move. Therefore it has a property that it does not flow.

20. Write a sentence like the above but for a gas.21. Complete the sentences:

In gases, the forces between particles have _____ strength, leading to a structure which has _____ gaps between particles. Therefore, gases have a property that they can be ______.

22. Write a sentence like the above for solids and liquids.23. A student says “a property of solids is that they have strong forces of attraction between particles.”

Explain why the student is wrong.24. When you put a knife into a liquid, you separate particles away from each other. Explain why it is

easier to do this in a liquid than a solid. 25. What name did Democritus give the tiny units of matter?26. Why do we talk about particles instead of atoms when explaining the states of matter?27. Fluids are substances that can flow and be poured. Which two states of matter are fluids?28. Below is the start of a “refutation paragraph.” This is a paragraph that explains why something is

wrong. Complete the paragraph.Some people think that liquids can be compressed. They are wrong. Liquids cannot be compressed because……

29. Look at the diagram, what will happen when each piston is pushed?

30. A child is playing with a bucket of sand. She pours the sand into a pile. Her father says “look the sand is flowing it must be a liquid.” Explain why the father is wrong.

31. A chocolate bunny is taken from the fridge and left out on a sunny windowsill. As it heats up it begins to change shape. Explain, using particles, why it had a fixed shape in the fridge, but began to change shape once it got hot.

Lesson 2: Diffusion

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I am learning how to describe the process of diffusion to explain how it works in different substances

If someone sprays deoderant in a room the scent spreads around the room. It is smelled by the people nearest to it first and those furthest away last. The people nearest also smell a stronger scent that those further away. This happens because the scent particles diffuse. Diffusion is the movement of a substance from an area of high concentration to an area of low concentration. Once diffusion has happened, the particles are spread out evenly. The reason diffusion can happen is because of kinetic theory. Kinetic theory is the idea that all particles are moving constantly. In a liquid and a gas they can move and flow and change position. In a solid the particles still move, but do not change position. Because of this, diffusion only really happens in gases and liquids, and is much faster in gases than liquids. If you put a bit of ink in some water, eventually the ink particles will spread through the whole water, but all the water particles need to move out their way for them to spread out. In a gas, there are such big spaces between the particles, that it is easy for new particles to move through the gas. 32. Draw two boxes on your page, one with five gas particles and one with three.33. Which one has a higher concentration of gas particles? Explain your answer.34. This box has two ends, A and B. Which end has a higher concentration of gas particles?

35. Diffusion is allowed to take place. A student says that at the end of the diffusion, the box will look like this:

Explain why the student is wrong.36. Draw a diagram showing what the box should look like. 37. Why is diffusion faster in gases than liquids?38. What is a fluid? Which two states are fluids?39. Someone is frying bacon in the food tech classroom down the corridor and around the corner from

the science lab. Use particle and kinetic theory to explain how you can smell the bacon cooking whilst sat at your desk in science.

Lesson 3: Changes of stateI am learning what happens when substances are heated to explain how changes of state occur

By heating and cooling different substances you can change their state. Heating goes from solid liquid gas and cooling goes in the other direction.

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40. Draw a particle diagram for a substance which is a solid.41. Draw a diagram for what that substance looks like once it has been melted.42. Draw a diagram for what that substance looks like once it has been boiled.43. A liquid is cooled down. What could happen to it?44. A liquid is heated up. What could happen to it?45. A student says that when a liquid boils, the particles get bigger. The student is wrong. Explain why. 46. In terms of their properties, what are the main differences between solids, liquids and gases?The melting point of a substance is the temperature at which it turns from a solid to a liquid when heated, or a liquid to a solid when cooled. The boiling point of a substance is the temperature at which it turns from a liquid to a gas when heated or a gas to a liquid when cooled. 47. Ice has a melting point of 0°C. Liquid water has a boiling point of 100°C.

a. What temperature does solid ice turn to liquid water?b. What temperature does steam turn to liquid water?c. What temperature does liquid water turn to ice?d. Some water is at 50°C. What state is it in?e. Some water is at -20°C. What state is it in?f. What temperature would water have to be at before it could be compressed?g. A sample of water does not flow. What temperature could it be at?

You can use these temperatures and a number line to work out the state of a substance at any given temperature. Your teacher will model with you how to do this. Room temperature is around 21°C.48. Ethanol has a melting point of -115°C and a boiling point of 78°C. What state is ethanol at room

temperature? 49. Copper has a melting point of 1085°C and a boiling point of 2580°C. What state is copper at room

temperature? 50. Mercury has a melting point of -39°C and a boiling point of -357°C. What state is mercury at room

temperature?51. Argon has a melting point of -189°C and a boiling point of -186°C. What state is argon at room

temperature? 52. Caesium has a melting point of 29°C and a boiling point of 685°C. What state is caesium at room

temperature?53. A substance has particles arranged in a fixed and regular pattern. What state is this substance?54. The substance is heated. A student thinks that the particles increase in size. Explain why the

student is wrong. Heating and cooling curves

A heating curve is a way of showing how the temperature of something changes as it is heating up. A cooling curve shows how the temperature of something changes as it cools down. First, we will do a heating curve by using a Bunsen to heat up water. Your teacher will show you how to do this and how to record your results in a table. Below is a table with some sample data that we will use to draw a graph.With your teacher, you will draw and label a graph to show this information.

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Time (minutes

)

Temperature (°C)

0 211 312 403 524 615 706 797 908 959 98

10 9911 10012 10013 100

We can do the same experiment, but for cooling down substances like salol (a waxy substance). Some example results are below

As before, you will draw a graph with your

teacher:

55. The melting point of the substance was 42oC. Look at your graph and describe what happens to the temperature when it reaches the melting point.

56. Draw a particle diagram of salol above and below 42oC.57. At what temperature will solid salol start to flow? Explaining what happens at the melting and boiling point

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Time (min) Temperature (ºC)

0 651 602 573 544 515 486 457 428 429 42

10 4211 3912 3613 34

Salol

When energy is added to a substance (and we will learn more about energy later), its temperature increases. However, when it gets to its melting or boiling point its temperature does not increase. This is because all of the energy is used to help break the forces between the particles. So if you heat up some liquid water, when it hits 100oC it will stay at that temperature for a little while as it turns into steam. The energy from the Bunsen burner is causing the particles to break apart from each other. It’s a bit more complicated than that, and even more complicated for cooling, but for the minute that’s all we need to know. Annotate the diagram below as your teacher explains why the graph changes shape.

For each of the questions below, pick one or two letters. The first one has been done for you58. Between which letters is melting taking place?

Answer: B and C59. At which letter does boiling start to take place?60. At which letter is the substance at its hottest?61. At which letter is the substance at its coldest?62. Between which letters is the substance a liquid and starting to heat up?63. Between which letters is the substance a solid and starting to heat up?64. Between which letters is the substance a gas and starting to heat up?65. At which letter do strong forces of attraction start to get broken?

Lesson 4: Gas PressureI am learning about gas pressure so I can predict how different conditions affect gases

As we have seen, gases are free to move around because the forces that hold them together are weak. If you put gas particles in a container like a balloon, they collide with (bump into) the walls of the container. In a balloon, this causes the balloon to inflate and get bigger. If you put a bit of

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solid in a balloon this wouldn’t happen because the particles don’t move around or push on the sides of the balloon. This colliding with the walls is called gas pressure. More collisions means more pressure.66. What is gas pressure?67. If I put a marble inside a balloon, why doesn’t the balloon inflate?68. If I put some liquid water inside a balloon, why doesn’t the balloon inflate?69. What temperature would I have to raise the liquid water to before the balloon will inflate?There are three ways to change the pressure:

1. Increasing the number of gas particles increases the pressure, so if I blow more air into a balloon, it inflates more. This is because there are more particles to collide with the sides of the balloon.

2. Increasing the temperature increases the pressure so if I warm up a balloon, it increases in size. This is because when I heat it up, the gas particles move faster. They collide more often with the walls of the balloon, and it inflates more.

3. Decreasing the size of the container increases the pressure, so if I squeeze a balloon too much it will burst. This is because the particles have less space to move around with and bump into the sides of the balloon more often.

We are going to practise the information above using some sentence builders. Your teacher will model how to do the first one:70. If a gas is heated up, the particles…71. If a gas is heated up, the pressure…72. If a gas is heated up, the pressure…because the particles…therefore they…73. If a gas is cooled down, the pressure…because the particles…therefore they…74. There are more collisions in a hot gas because…75. Small containers have…because the particles…therefore they…76. If particles are added to a balloon, the pressure…because the particles…77. If particles are taken out of a balloon, the pressure…because the particles…78. Increasing temperature increases collisions because…

Increasing temperature increases collisions but…Increasing temperature increases collisions therefore…

Your teacher will now demonstrate the exploding can.79. The exploding can

a) What did you observe happen as the can was heated?b) What has happened to the number of air particles in the can?c) A student says the pressure of the exploding can increases because the can is made smaller in

volume. Explain why the student is wrong. d) How else could the pressure in the can be increased other than by increasing the temperature?

80. Aerosol cans like deodorant and hairsprays contain the liquid and a gas, under pressure. When the top is pressed, the pressure of the gas pushes the liquid out of the can. They often contain warnings about storing in direct sunlight.

a. Explain why it is important to not store a deodorant can in direct sunlightb. Explain why once the gas is released you can smell it all around the roomc. Explain why the pressure in the can decreases the more it is used

81. The picture shows a hot air balloon. Explain, in terms of particles, what happens inside the balloon when the operator lights the burner and heats up the air.

Part 2: Separation techniquesLesson1: DissolvingI am learning about how to form a solution from a solute and a solvent by dissolving

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When you add salt to liquid water it looks like the salt vanishes. You can explain what happens using particles. When salt is added to water, the particles all break away from each other and move into the water.

We have special scientific words to describe what is happening. We call the salt the solute, and the water is called the solvent. When the forces in the solute break up and the particles go into the solvent, we call that process dissolving. The substance at the end which has the solute and solvent all mixed up is called a solution.Solute: the solid Solvent: the liquidDissolving: when the forces in the solute break up and it mixes with the solventSolution: the solute and solvent after dissolving has happened82. A student says that when a solute dissolves in a solvent, the particles break. Explain why the

student is wrong.83. A student takes some sugar and adds it to some water. The student stirs it and can not see the

sugar any more. a. Name the soluteb. Name the solventc. What happens when the solute is mixed with the solvent?d. What is the sugar water at the end called?

84. A student adds sand to water and mixes it. She can still see the sand at the end.a. Explain why sand is a solid even though it looks like it can flowb. Has the sand dissolved?c. Explain your answer, using the words “particles” and “forces” d. Sand has a melting point of 1650°C. Draw a particle diagram of sand at 1500°C.e. Draw a particle diagram of sand at 2000°C.f. Explain why sand cannot be compressed.

Soluble and insoluble

In the previous question, we saw that sand does not dissolve in water. We call it insoluble in water. Salt does dissolve in water so we call it soluble in water. Different substances are soluble in different solvents. For example, nail varnish is insoluble in water, which is why it doesn’t come off if you just wash your hands. However, it is soluble in a special solvent called acetone, so nail varnish remover contains lots of acetone. That’s why if you are saying something is soluble or insoluble, it’s best to be clear about what solvent you are discussing. 85. Sand does not dissolve in water. Does that mean it is insoluble? Explain your answer.86. Draw a particle diagram of a grain of sand.87. Draw a particle diagram of that grain of sand in some water. 88. Sugar dissolves in water but does not dissolve in oil. Describe sugar using the words soluble and

insoluble.89. Sugar’s melting point is 186°C. If sugar is at 300°C and is slowly cooled down, what temperature

will it turn into a liquid at?90. What is the name for this process?91. Some ice is heated up from -20°C. The temperature gradually increases. At a certain point, the

temperature stops increasing for a little while. What temperature is this?92. In terms of particles and forces, what is happening?93. The ice eventually melts to form water and is then boiled into a gas. What is the name of this gas?94. The gas is passed into a balloon and the balloon inflates. Why does the balloon inflate?

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95. More gas is put into the balloon. What does this do to the pressure in the balloon? Explain your answer.

96. How else could the pressure in the balloon be changed? Both salt and sugar are soluble in water. If I have a beaker with 100cm3 of water in it, I can dissolve about 36g of salt in it. However, if I had another beaker with 100cm3 of water in it, I could dissolve around 90g of sugar in it. This is because even though they are both soluble, sugar is more soluble. We say it has a higher solubility. 97. There are two solutes, A and B. I can dissolve 15g of A in 100cm3 of water and 20g of B in 100cm3.

a. Which one has a higher solubility?b. If I had 200cm3 of water, how much A could dissolve in it?c. If I add 20g of A to 100cm3 of water, how much will be left over?d. 12g of C can dissolve in 50cm3 of water. Compared to A and B, how soluble is it?

Lesson 2: The conservation of massI am learning about the conservation of mass so I can explain how mass changes when dissolving solutes

The conservation of mass the most important rule in chemistry. The conservation of mass states that particles cannot be created or destroyed but they can be moved around. Your teacher will demonstrate to you how the mass of a solution is the same as the mass of the solvent + the mass of the solute. We can also use the conservation of mass for changes of state. When a liquid boils, the particles aren’t destroyed, they just rearrange into a new structure. When a solid melts, the particles aren’t destroyed, they just rearrange into a new structure. 98. A student adds 10g of salt to 100g of water and stirs it. The student says “I cannot see the salt

anymore, so it has been destroyed.” Explain why the student is wrong.99. What is the mass of the solution that has been formed? 100. Some water is boiled until none of it can be seen any more. A student says that the water has

been destroyed. Is the student correct? Explain your answer. 101. A student has 100g of ice. The student lets it melt into water. What mass of water will there be at

the end? Explain your answer.102. Sarah dissolves 3g of copper sulphate in 100g of water. Calculate the mass of solution.103. Matt dissolves salt in 150g of water to form a solution of 177g. Calculate the mass of the salt used.104. What is the law of conservation of mass?105. A student has 200g of water. They boil the water and trap the steam in a balloon which weighs 5g.

What will the mass of the balloon with all the steam in it be? Explain your answer. 106. The student lets the balloon cool down and the steam starts to condense. What happens to the

pressure in the balloon as the steam condenses? Explain your answer. 107. A student has 10g of liquid water in a glass. They spill the water on the table and it spreads out.

They say that it now weighs more as it has spread out. Explain why the student is wrong.

Lesson 3: mixturesI am learning about mixtures so I can explain how they are separated

When a golf ball is added to water, it does not dissolve. The golf ball and the water do not bond with each other and the golf ball can be removed using a net. The golf ball and the water are called a mixture. This is when you have different things together which are not bonded to each other. There are lots of different types of mixtures. Sand and water together is also a mixture. Even a solution of salt and water is a mixture, because the salt is still salt, its just mixed in the water. The salt particles do not bond with the water. 108. A student adds 5g of sugar to 100g of water and stirs it. They can’t see the sugar any more. They

say that “the sugar has all gone.” Explain why they are incorrect.109. What is the mass of the solution.110. The sugar-water is a mixture. What is a mixture?111. Another student says that the sugar has bonded with the water. Is this correct? Explain your

answer. Normally, mixtures are quite easy to separate, but different mixtures need to be separated in different ways.

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Mixtures are often compared to pure substances. These are substances that only have one type of particle in them. So because sugar only has sugar particles in it, it is pure. Liquid water is also pure if it doesn’t have anything else in it. When the sugar is dissolved in the water, the solution is not pure as it has water and sugar particles.

How to separate mixtures

Depending on the states of matter that are mixed they need different techniques to separate them.Separation technique

Mixture to separate Example

Filtering An insoluble solid and a liquid Sand and waterSeparating by hand

Two solids Smarties and sugar

Using a magnet A magnetic substance from a non-magnetic substance

Iron nails and sand

Evaporation A soluble solid (solute) from a liquid (solvent)

Salt and water

Distillation Two liquids with different boiling points Ink and waterChromatography Two or more soluble substances Different colours in an ink

pen

Filtering

Filter paper is paper that has tiny holes. When sand is added to water, the sand stays as grains. These grains are too big to fit through the holes in the paper. Water particles are small enough to fit through. This means that if you pass sandy water through filter paper, the water will go through but the sand will not.

This does not work for solutions. In a solution, the particles come away from each other, so can fit through the holes.112. Explain why a student could use filter paper to separate a mixture of rice and water113. Explain why a student could not use filter paper to separate a solution of sugar and water114. A student adds 30g of sand to 100g of water. The mixture has a mass of 130g. The student filters

the mixture.

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a. What is the residue?b. How much does the residue weigh?c. What is the filtrate? d. How much does the filtrate weigh?e. Draw a particle diagram of the residue and the filtrate

115. A student dissolves salt in water and passes it through filter paper. Will any salt be found in the filter paper? Explain your answer.

116. A student adds 50g of salt to 100g of water. Only 20g of salt dissolves. The student filters the salty water.

a. What mass of salt did not dissolve?b. Why can that salt be separated by filtration?c. What will the mass of the residue be?d. What will the mass of the filtrate be?

117. Answer the questions below in you exercise booka. Define a pure substanceb. Define a mixturec. Tap water naturally has minerals dissolved in it. Is it a pure substance? Why? d. Describe the arrangement and motion of the particles in a bar of pure Iron. (Note: include a

diagram with at least 9 particles)118. Bill has bought a wedding ring for his fiancé. The jeweller told him it was pure gold but the ticket

says it contains 13% copper and the rest is gold. a. Is it a pure substance or a mixture? Why? b. What percentage of gold is in Bill’s ring?

119. Without looking back in your booklet, sketch in pencil a graph to show how the temperature of ice changes as it warms up from -20°C to 120°C

120. Once you are finished your sketch, go back in the booklet and use your purple pen to make corrections.

121. Label the graph with the labels: melting point, boiling point122. Energy is still being transferred to the ice when it is melting, but the temperature does not

change. Where is the energy going?Evaporation

When a solute is dissolved in a solvent, it cannot be removed by filtering. What we can do, is allow the solvent to evaporate. Evaporation is like boiling, but it normally happens without you having to do lots of heating. If you leave a glass of water on a window sill, the water will evaporate by itself, without you having to heat it up to 100°C. When it does this, anything dissolved in the water is left behind at the end. In the lab, we call this evaporation or crystallisation and we use an evaporating dish. Often we boil off a bit of the solvent first just to get things going. 123. A student dissolves some salt in some water. Why is this

called a mixture?124. Why is this no longer called a pure substance?125. Why can they not use filtration to separate the salt from

the water?126. The student uses evaporation to separate the mixture.

What equipment should they use?127. How does evaporation separate the mixture? Use the

words below in your answer.Solute, solvent, particles, evaporates

128. The student dissolves 40g of salt in 150g of water. They then evaporate the solution. What mass of salt can be collected? Explain your answer.

Rock salt

Rock salt is a type of salt that is a mixture of salt (like the kind we eat) and bits of sand and dirt and rock. We use it to grit roads in the winter and stop them getting too icy. We can turn it into pure salt by first mixing it with water, then filtering it and then evaporating it.129. A student has 100g of rock salt. It is a solid. Draw a particle diagram of rock salt.

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130. Explain why rock salt is not considered a pure substance.131. The student mixes the rock salt with water. Complete the sentence stems:

The salt dissolves because…The salt dissolves but…The salt dissolves therefore…

132. What phrase can be used to describe the substances which do not dissolve in water?133. The student filters the resulting mixture. What substances are left as the residue?134. What is the filtrate in this case?135. Explain why some substances pass through the filter paper and others don’t.136. How can the student separate the substances in the filtrate?137. At the end, the student is left with 35g of pure salt. What was the mass of the dirt and sand and

rock in the original rock salt?Distillation

Recap questions:138. When ink and water are added to each other you get a mixture. What is a mixture?139. Why can they not be separated by filtration?140. The mixture cannot be compressed. Explain why141. If a drop of ink is added to water, it eventually spreads out through the whole liquid. What is the

name for the process by which this happens?142. Describe what occurs, using the terms high concentration and low concentration in your

answer143. How could you speed up this process? 144. Explain your answer. In order to separate mixtures with two different liquids, we use distillation. This is a bit more complicated than the techniques we have used so far. Let’s say you have a mixture of water and ethanol. Water boils at 100°C. The ethanol boils at 78°C. If you heat the mixture up to 78°C, then the ethanol will boil, but the water will stay as a liquid. The ethanol gas can then be moved away from the liquid water and cooled down. It can then condense and be collected. Your teacher will demonstrate the process using the equipment below.

145. Why can a 146. What temperature should you be careful to not go above?147. Where does the ethanol gas go once it is formed?148. What is the name for the process of how the ethanol spreads out?149. A student describes the separation of orange squash from water as below. Identify as many

mistakes as you can.First, the pure substance is heated up. At 50°C the water melts and turns into a gas. It goes up and moves away from the orange squash. This is called gas pressure. It then goes into the funnel where it gets colder and freezes back into a liquid.

150. Write a correct version of the description above.

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Chromatography

If you take red ink and mix it with blue ink, you will get a purple ink as a mixture. We can separate these inks using chromatography. In chromatography, we say there are two phases:Mobile phase: the bit that moves, the solventStationary phase: the bit that doesn’t move, the paper If you put the ink on the paper, and the paper in the solvent, the solvent will be absorbed through the paper. The inks then get dragged along as the solvent moves. Some inks get dragged along more, and others get dragged along less. This lets us see the different inks in the mixture. This process is called chromatography.

151. Mixing yellow and blue ink can make a green ink. Explain how green ink can be separated using chromatography. Use the structure:First, the…Then, a…Continue like this until you have a paragraph explaining how it is done.

152. Why is the line drawn in pencil? Use the word “insoluble” in your answer. 153. Why does the solvent need to be lower than the pencil line?The paper at the end is called the “chromatogram” and it shows the number of inks in different mixtures. You can put lots of different inks on one piece of chromatography paper and compare which colours they have in them.

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154. A student sets up a chromatogram as shown in the chromatogram 1. They have made two mistakes. What are the two mistakes, and why will they ruin the experiment?

155. A student tests four inks in chromatogram 2. How many different colours is X made of?156. Our of A, B and C, which colours does X also have?157. Why can A be called pure but X can’t?

158. Chromatogram 3 has four different colours, which can be found in soft drinks. We can compare them to some colours which we know are safe to figure out if they are safe. For example, B has two colours, and each of those colours are “safe” as they line up with spots in the “safe colours” bit.

a. Which other colour out of A, B, C and D is safe?b. Why is D not sage?c. How could A be made safe?d. How many colours in total are present across A, B, C and D?

Overview of separation questions:159. How can a mixture of green and red tennis balls be separated?160. What property is their separation based on?161. How can a mixture of salt and water be separated?162. Why can salt and water not be separated by filtration?163. 51g of solute A can dissolve in 150cm3 of water. 58g of solute B can dissolve in 150cm3 of water.

Which solute is has a higher solubility? 164. How can iron and sulfur be separated?

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165. Why can they not be separated by filtration?166. Why can sand and water not be separated by hand?167. How can a mixture of two liquids be separated?168. Sand and water are separated by filtration because…

Sand and water are separated by filtration but…

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